Display device, mask, and method for manufacturing display device

ABSTRACT

A display device includes: a plurality of pixel-region mask spacers disposed in a pixel region where a plurality of pixels are disposed; a plurality of frame-region mask spacers disposed in a frame region outside the pixel region so as to surround the pixel region; and a common layer disposed on the plurality of pixel-region mask spacers, the common layer being common to the plurality of pixels, wherein the common layer comprises an end that has undulations in a plan view.

TECHNICAL FIELD

The present invention relates to a display device, a mask, and a methodfor manufacturing the display device.

BACKGROUND ART

As described in Patent Literature 1, producing a display device usesmasks for forming individual layers onto a substrate. These masksinclude a fine metal mask (hereinafter referred to as an FMM) forforming a layer selectively for each pixel, and a common metal mask(hereinafter referred to as a CMM) or open mask (hereinafter referred toas a CMM) for forming a common layer common to all the pixels. In thefilm formation, the substrate and each mask are joined together closelyby a magnetic force from a magnetic-force generating source, such as amagnet on the substrate backside.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Laid-Open No.2009-259404 (published on Nov. 5, 2009)

SUMMARY OF INVENTION Technical Problem

When the mask and substrate are joined together closely, the position ofthe mask can shift due to various factors, including a magnetic force, amisalignment, a tolerance of the substrate or mask, and a mispositionedalignment mark. An FMM has openings that correspond to pixels and aredisposed in only necessary pixels. The FMM, when joined closely with thesubstrate, is held by mask spacers disposed inside and outside a pixelregion provided with a plurality of pixels. A CMM in contrast has anopening that opens the entire pixel region. The CMM thus has a largeropening area than the FMM, and is held by only mask spacers outside thepixel region when joined closely with the substrate.

In occurrence of a mask position shift as described above, the CMM hasan opening end more easily bent toward the substrate by its own weightor a magnetic force than the FMM. The CMM opening end bent toward thesubstrate by a magnetic force easily come into contact with mask spacersarranged in the direction of the position shift. The CMM opening end canhave sticking foreign substances, such as a film consisting of depositedmaterials resulting from film formation, and a residue remainingunremoved after mask cleaning. These sticking foreign substancestransfer to the mask spacers upon contact of the CMM opening end to themask spacers. Such foreign substances cause dark spots and otherproblems, degrading the reliability of the display device.

In some cases, disposed between the interior mask spacers and exteriormask spacers is a region where a cathode is in contact with a wirerouted in a TFT layer including TFTs that drive light-emitting elements.The opening end of a typical CMM is flush and has in plan view a linearshape, as described in Patent Literature 1. If the opening end of such aCMM shifts to the outside of the pixel region, a common layer formedusing the CMM extends out to the outside of the pixel region uniformly.The common layer consequently closes the inside of the contact region,increasing the area of a region where the cathode and the routed wirecannot be in contact with each other, and increasing contact resistance.Such a problem leads to reliability degradation in the display device.

Solution to Problem

A display device according to one aspect of the present inventionincludes the following: a plurality of pixel-region mask spacersdisposed in a pixel region where a plurality of pixels are disposed; aplurality of frame-region mask spacers disposed in a frame regionoutside the pixel region so as to surround the pixel region; and acommon layer disposed on the plurality of pixel-region mask spacers. Thecommon layer is common to the plurality of pixels. The common layer hasan end that has undulations in plan view.

A mask according to a further aspect of the present invention has anopening that opens a pixel region where a plurality of pixels aredisposed. The mask is used to form a common layer common to theplurality of pixels. The opening has an opening end that has undulationsin plan view.

A method for manufacturing a display device according to a still furtheraspect includes forming a plurality of frame-region mask spacers in aframe region outside a pixel region so as to surround the pixel region.The pixel region is provided with a plurality of pixels. The method alsoincludes the following: forming a plurality of pixel-region mask spacersin the pixel region; and bringing a mask into abutment with theplurality of frame-region mask spacers to form a common layer common tothe plurality of pixels onto the plurality of pixel-region mask spacers.The mask has an opening that opens the pixel region and whose openingend has undulations in plan view.

Advantageous Effect of Invention

In the formation of the common layer, the aspects of the presentinvention achieve a margin between the opening end of the mask, used toform the common layer common to the pixels, and the pixel-region maskspacers. In the formation of the common layer, the aspects thus preventcontact between the mask opening end and the pixel-region mask spacersor frame-region mask spacers even when the mask, used to form the commonlayer common to the pixels, is shifted to any direction with respect tothe pixel-region mask spacers. This avoids a foreign substance fromsticking to the pixel-region mask spacers or frame-region mask spacerseven when it sticks to the mask opening end. In the formation of thecommon layer, the aspects of the present invention reduces the area of aportion between the pixel-region mask spacers and the frame-region maskspacers that is not covered with the mask. In some cases, disposedbetween the pixel-region mask spacers and the frame-region mask spacersis a region where one of the electrodes of each light-emitting elementis in contact with a wire routed in a TFT layer including TFTs thatdrive the light-emitting elements. Accordingly, in the formation of thecommon layer, such area reduction achieves a contact region even whenthe mask, used to form the common layer common to the pixels, is shiftedtoward the frame region with respect to the pixel-region mask spacers.The aspects consequently offer a display device more reliable than everbefore, a mask with which such a more reliable display device can bemanufactured, and a method for manufacturing such a more reliabledisplay device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart illustrating an example method for manufacturing adisplay device according to one embodiment.

FIG. 2 is a cross-sectional view of the configuration of a pixel regionof the display device according to the embodiment.

FIG. 3 is a cross-sectional view of the configuration of a frame regionand its neighborhood of the display device according to the embodiment.

FIG. 4 is a plan view of an example mask that is used to form a commonlayer of the display device according to the embodiment.

FIG. 5 illustrates how the common layer of the display device accordingto the embodiment is formed using the mask illustrated in FIG. 4.

FIG. 6 schematically illustrates the relationship between mask spacersand an opening end of the mask illustrated in FIG. 4.

FIG. 7(a) schematically illustrates in plan view where the opening endof the mask in FIG. 4 shifted toward the pixel region is located inrelation to pixel-region mask spacers. FIG. 7(b) schematicallyillustrates in plan view where the opening end of the mask in FIG. 4,with its protrusions between the pixel-region mask spacers adjacent to aframe region being shifted toward the pixel-region mask spacerssandwiching the protrusions, is located in relation to the pixel-regionmask spacers.

FIG. 8(a) schematically illustrates in cross-sectional view where theopening end of the mask in FIG. 4 disposed properly with respect to thepixel-region mask spacers is located in relation to the pixel-regionmask spacers. FIG. 8(b) schematically illustrates in cross-sectionalview where the opening end of the mask in FIG. 8(a) shifted toward thepixel region is located in relation to the pixel-region mask spacers.

FIG. 9 illustrates in plan view where the opening end of the mask inFIG. 4 shifted toward the frame region is located in relation to thepixel-region mask spacers.

FIG. 10(a) schematically illustrates in cross-sectional view where theopening of a mask (CMM) whose opening end has a linear shape in planview and that is disposed properly with respect to the pixel-region maskspacers is located in relation to the pixel-region mask spacers. FIG.10(b) schematically illustrates in cross-sectional view where theopening end of the mask in FIG. 10(a) shifted toward the pixel region islocated in relation to the pixel-region mask spacers. FIG. 10(c)schematically illustrates in cross-sectional view what happensunfavorably when the common layer is formed in the situation shown inFIG. 10(b) and is then sealed with a sealing layer.

FIG. 11 illustrates in plan view where the opening end of the mask inFIG. 10(a) shifted toward the frame region is located in relation to thepixel-region mask spacers.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be detailed. Componentshaving the same functions as previously described components will bedenoted by the same signs and will not be elaborated in the followingembodiments.

Outline of Configuration of Display Device and Outline of How toManufacture the Same

FIG. 1 is a flowchart illustrating an example method for manufacturing adisplay device 2 according to this embodiment. FIG. 2 is across-sectional view of the configuration of a pixel region (displayregion) of the display device 2 according to the embodiment. FIG. 3 is across-sectional view of the configuration of a frame region NA and itsneighborhood of the display device 2 according to the embodiment. Theterm “in the same layer” hereinafter refers to that one layer is formedin the same process step (film formation step) as another thing. Theterm “in a lower position than” hereinafter refers to that one layer isformed in a process step anterior to a process step of forming thecomparative layer. The term “in a higher position than” hereinafterrefers to that one layer is formed in a process step posterior to aprocess step of forming the comparative layer.

A method for manufacturing the display device 2, which is flexible,includes the following process steps in sequence as illustrated in FIGS.1 to 3: Step S1 of forming a resin layer 12 onto a translucent supportsubstrate (e.g., a mother glass substrate); Step 2 of forming a barrierlayer 3; Step S3 of forming a TFT layer 4; Step S4 of forming alight-emitting element layer 5; Step S5 of forming a sealing layer 6;and Step S6 of temporarily attaching a protective, upper-surface film tothe sealing layer 6.

The method also includes the following process steps in sequence: StepS7 of removing the support substrate from the resin layer 12 by laserlight irradiation or other methods; Step S8 of attaching a lower-surfacefilm 10 to the lower surface of the resin layer 12; Step S9 of cutting astack of the lower film 10, resin layer 12, barrier layer 3, TFT layer4, light-emitting-element layer 5, and sealing layer 6 into a pluralityof pieces; Step S10 of removing the upper film from the resultantpieces; Step S11 of attaching a function film 39 to the resultantpieces; and Step S12 of mounting an electronic circuit board (e.g., anIC chip and an FPC) onto a part (a terminal) of a region (a frame regionNA; see FIG. 3) that is outside pixel regions DA (see FIG. 3) where aplurality of pixels are disposed. Steps S1 to S12 are performed by anapparatus that manufactures the display device (including a filmformation apparatus that performs Steps S1 to S5).

The resin layer 12 is made of, but not limited to, polyimide. The resinlayer 12 can be replaced with a set of two resin films (e.g., polyimidefilms) and one inorganic insulating film sandwiched between these resinfilms.

The barrier layer 3 prevents foreign substances, such as water andoxygen, from entering the TFT layer 4 and light-emitting-element layer5. The barrier layer 3 can be composed of a silicon oxide film, asilicon nitride film, or a silicon oxide nitride film, all of which areformed through CVD, or can be composed of a stack of these layers.

The TFT layer 4 includes the following components: a semiconductor film15; an inorganic insulating film 16 (a gate insulating film) in a higherposition than the semiconductor film 15; a gate electrode GE and gateline GH in a higher position than the inorganic insulating film 16; aninorganic insulating film 18 in a higher position than the gateelectrode GE and the gate wire GH; a power-source wire CE in a higherposition than the inorganic insulating film 18; an inorganic insulatingfilm 20 in a higher position than the power-source wire CE; a sourcewire SH in a higher position than the inorganic insulating film 20; anda flattening film 21 (an interlayer insulating film) in a higherposition than the source wire SH.

The semiconductor film 15 is made of, but not limited to,low-temperature polysilicon (LTPS) or oxide semiconductor (e.g.,In—Ga—Zn—O semiconductor). Together with the gate electrode GE, thesemiconductor film 15 forms a transistor (herein a TFT). Although thetransistor has a top-gate structure in FIG. 2, it may have a bottom-gatestructure.

The gate electrode GE, gate wire GH, power-source wire CE, and sourcewire SH are each composed of a monolayer film of metal including atleast one of, for instance, aluminum, tungsten, molybdenum, tantalum,chromium, titanium, and copper; alternatively these components are eachcomposed of a laminated films of these materials. The TFT layer 4 inFIG. 2 includes one semiconductor layer and three metal layers.

The inorganic insulating films 16, 18, and 19 each can be composed of asilicon oxide (SiOx) film or a silicon nitride (SiNx) film, both ofwhich are formed through CVD, or each can be composed of a laminatedlayer of these films. The flattening film 21 can be made ofphotosensitive organic material that can be applied, such as polyimideor acrylic.

The light-emitting-element layer 5 includes the following components: ananode 22 in a higher position than the flattening film 21; an edge cover23 that is insulating and covering the edge of the anode 22; anelectroluminescence (EL) layer 24 in a higher position than the edgecover 23; a cathode 25 in a higher position than the EL layer 24; andmask spacers 31 and 32. The light-emitting element layer 5 may alsoinclude a capping layer, such as an organic capping layer or aninorganic capping layer, in a higher position than the cathode 25.

The edge cover 23 contains an organic material (such as polyimide oracrylic) patterned through photolithography after application.

For each pixel, the anode 22, EL layer 24, and cathode 25 constitute alight-emitting element ES (e.g., an organic light-emitting diode or OLEDfor short, and a quantum-dot light-emitting diode or QLED for short) inthe light-emitting element layer 5. The light-emitting element ES iscontrolled by a pixel circuit disposed in the TFT layer 4.

The anode 22 is a patterned electrode provided in the form of an islandfor each pixel. The cathode 25 is a common electrode provided in a flatmanner and common to all the pixels, and is disposed all over the pixelregions DA rather than provided individually for each pixel.

The cathode 25 is formed through vapor deposition mainly, whereas theanode 22 is formed through sputtering mainly. The cathode formationthrough vapor deposition uses a deposition mask, which is herein an openmask called a common metal mask (CMM) having an opening that opens theentire pixel region DA.

The EL layer 24 is composed of, but not limited to, a set of thefollowing function layers sequentially stacked from below: a holeinjection layer, a common hole transport layer, an island-shaped holetransport layer, a light-emitting layer, a hole blocking layer, anelectron transport layer, and an electron injection layer. Thelight-emitting layer is provided in the form of islands in the openingsof the edge cover 23 (i.e., for each pixel) for instance, through avapor deposition method or an ink-jet method.

Forming a light-emitting layer of an OLED uses vapor deposition with adeposition mask, which is herein a fine metal mask (FMM) for instance,thus forming a vapor-deposited layer in the form of islands. Forming alight-emitting layer of a QLED uses ink-jet application of a solventcontaining diffused quantum dots for instance. For an OLED that emitswhite light, or in forming a common light-emitting layer common to aplurality of pixels, an open mask called a common metal mask (CMM) canbe used as a deposition mask.

The island-shaped hole transport layer is in the form of islands formedthrough vapor deposition with an FMM. The other function layers areprovided either in the form of islands or in a flat manner as commonlayers formed through vapor deposition with an FMM or CMM. Thesefunction layers each may be an organic layer of organic material or aninorganic film of inorganic material.

The capping layer is provided in a flat manner as a common layer formedthrough vapor deposition with a CMM. For instance, the capping layer mayhave a stacked structure of, in sequence, an organic capping layer oforganic material and an inorganic capping layer of inorganic material;alternatively; the capping layer ay be composed of only one of the twolayers.

One or more of the hole injection layer, common hole transport layer,island-shaped hole transport layer, light-emitting layer, hole blockinglayer, electron transport layer, and electron injection layer can beomitted; alternatively, another layer can be provided additionally.

For instance, the anode 22 is composed of a stacked layer of indium tinoxide (ITO) and silver (Ag) or is composed of a stacked layer of ITO andAg-containing alloy. The anode 22 reflects light. The cathode 25 can becomposed of a translucent conductor, such as a MgAg alloy (extremelythin film), an ITO, or an indium zinc oxide (IZO).

When the light-emitting element ES is an OLED, a drive current betweenthe anode 22 and cathode 25 rejoins holes and electrons within thelight-emitting layer, thus generating excitons. These excitons emitlight in the process of transition to a ground state. When the cathode25 transmits light, and the anode 22 reflects tight, the light from theEL layer 24 travels upward and goes out from the top. When the cathode25 reflects light, and the anode 22 transmits light, the light from theEL layer 24 travels downward and goes out from the bottom.

When the light-emitting element ES is a QLED, a drive current betweenthe anode 22 and cathode 25 rejoins holes and electrons within thelight-emitting layer, thus generating excitons. These excitons emitlight (fluorescent light) in the process of transition from a conductionband level of the quantum dots to a valence band level of the quantumdots.

The light-emitting-element layer 5 may include light-emitting elementsES (e.g., inorganic light-emitting diodes) other than OLEDs and QLEDs asdescribed above.

The mask spacers 31 are pixel-region mask spacers disposed in each pixelregion DA, as illustrated in FIG. 3. In addition, the mask spacers 32are frame-region mask spacers disposed in the frame region NA andsurrounding the pixel region DA. The mask spacers 31 are disposedbetween adjacent anode-exposed portions (openings of the edge cover 23where the anode 22 is exposed) in each pixel. In some embodiments, thepixel region DA may have dummy pixels surrounding display pixels, or mayhave display pixels alone. The anode-exposed portions in each displaypixel function as light-emission regions of the light-emitting elementES. To be specific, the mask spacers 31 are disposed in a predeterminedportion of the edge cover 23 so as to protrude toward the cathode 25(i.e., in a direction remote from the TFT layer 4). The mask spacers 31are not shown in FIG. 2.

The mask spacers 31 hold an FMM in film formation using the FMM. Themask spacers 32 hold the FMM in film formation using the FMM and hold aCMM in film formation using the CMM. The FMM is thus held by the maskspacers 31 and 32 in film formation (in other words, in joining togetherof a film and a target substrate closely). In addition, the CMM is thusheld by the mask spacers 32 in film formation (in other words, injoining together of a film and the target substrate closely).

The mask spacers 31 and 32 are made of photosensitive resin forinstance. The mask spacers 31 and 32 may be made of material identicalto or different from that of the edge cover 23.

The sealing layer 6 is translucent. The sealing layer 6 includes aninorganic sealing layer 26 covering the cathode 25, an organic bufferfilm 27 in a higher position than the inorganic sealing layer 26, and aninorganic sealing film 28 in a higher position than the organic bufferfilm 27. The sealing layer 6, which covers the light-emitting-elementlayer 5, prevents foreign substances, such as water and oxygen, frompenetrating the light-emitting-element layer 5.

Each of the inorganic sealing layers 26 and 28 is an inorganicinsulating film. Each of the inorganic sealing layers 26 and 28 can becomposed of a silicon oxide film, a silicon nitride film, or a siliconoxide nitride film, all of which are formed through CVD, or can becomposed of a stack of these films. The organic buffer film 27 is atranslucent organic film that flattens a film, and can be made oforganic material that can be applied, such as acrylic. The organicbuffer film 27 can be formed through ink-jet application for instance.To stop ink droplets, the frame region NA may have a frame-shaped bank33 and another frame-shaped bank (not shown) surrounding the bank 33, asillustrated in FIG. 3. The bank 33 can be formed at the same time usingthe same material as the edge cover 23 and mask spacers 31 and 32. Theother frame-shaped bank (not shown) around the bank 33 has a 2-plystructure consisting of lower and upper layers for instance. The lowerlayer can be made of the same material as the flattening film 21 andformed at the same time as pattern formation of the flattening film 21.The upper layer can be formed at the same time using the same materialas the edge cover 23 and mask spacers 31 and 32 for instance.

The lower film 10 is, but not limited to, a PET film attached to thelower surface of the resin layer 12 after the removal of the supportsubstrate, thus achieving a highly flexible display device. The functionfilm 39 serves as, but not limited to, at least one of an opticalcompensator, a touch sensor, and a protector.

The foregoing has described a flexible display device. Producing anon-flexible display device, which typically does not require formationof a resin layer and replacement of a base material, involves Steps S2to S5 of stacking layers onto a glass substrate, followed by Step S9 forinstance.

As described above, the display device 2 according to the embodiment hasat least one common layer disposed all over the pixel regions DA in aflat manner and common to all the pixels (i.e., a plurality of pixels).

FIG. 4 is a plan view of an example mask 71 that is used to form acommon layer of the display device 2 according to the embodiment. FIG. 5illustrates how a common layer 41 of the display device 2 according tothe embodiment is formed using the mask 71 in FIG. 4.

The mask 71 is an open mask called a CMM, which is used to form a commonlayer common to all the pixels as described above. As illustrated inFIGS. 4 and 5, the ask 71 has openings 72 each of which opens the entirepixel region DA that at least includes a display region where a displaypixel is disposed.

As illustrated in FIG. 4, the film formation requires a single mask 71for multiple pixel regions DA of the display device 2 on the supportsubstrate (mother substrate) that have been cut into pieces in Step S9,as described above. In some cases, the mask 71 may have only one opening72.

As illustrated in FIGS. 4 and 5, each opening 72 has an opening end 72 aprovided with undulations 73 that consist of depressions and protrusionsrepeatedly arranged in plan view. As illustrated in FIG. 5, theintervals (cycles) between the undulations 73, that is, the intervalbetween the adjacent protrusions of the undulations 73 and the intervalbetween the adjacent depressions of the same, are equal to, forinstance, the intervals between the mask spacers 31 (i.e., the distancebetween the adjacent mask spacers 31). In addition, the intervalsbetween the mask spacers 32 (i.e., the distance between the adjacentmask spacers 32) are smaller than the intervals between the mask spacers31. The example mask spacers 32 in FIG. 5 are arranged at half theintervals between the mask spacers 31. For instance, each mask spacer 31is a 1.0 to 2.0 μm high, tapered cylindrical column whose upper surface,which abuts on the FMM, is a circle that is 5 to 10 μm in diameter. Forinstance, each mask spacer 32 is a 1.0 to 2.0 μm high, taperedquadrangular prism whose upper surface, which abuts on the FMM and CMM,is a quadrangle (e.g., a square) having four sides each of which is 10to 15 μm long. Herein, the heights of the mask spacers 31 and 32 aremeasured with reference to the upper surface of the flattening film 21,which means that these heights are measured from the upper surface ofthe flattening film 21.

The opening end 72 a of the opening 72 (i.e., the undulations 73) has awavy shape in conformance with the arrangement of the mask spacers 31 soas to be away from the mask spacers 31 by equal to or greater than apredetermined distance. The undulations 73 are provided in such a mannerthat their protrusions are located between the mask spacers 31 adjacentto the frame region NA when the mask 71 and target substrate areoverlaid with each other.

The mask 71 is thus provided in such a manner that the protrusions ofthe undulations 73 are located between the mask spacers 31 adjacent tothe frame region NA when the mask 71 and target substrate are joinedtogether closely. Placing the mask 71 properly with respect to the maskspacers 31 provides equal to or greater than a predetermined distancebetween the undulations 73 and the mask spacers 31 adjacent to the frameregion NA.

The common layer 41 is disposed in the opening 72 of the mask 71. Thecommon layer 41 thus has at its end undulations 42 that correspond tothe undulations 73 of the mask 71 in plan view. That is, the end of thecommon layer 41 consists of depressions disposed along and facing theprotrusions of the undulations 73, and protrusions disposed along andfacing the depressions of the undulations 73. The undulations 42 thushave a wavy shape for instance corresponding to the undulations 73. Theintervals of the undulations 42 are identical to the intervals of theundulations 73 and equal to the intervals of the mask spacers 31. Thecommon layer 41 is disposed on the mask spacers 31 in such a manner thatthe depressions of the undulations 42 are located between the maskspacers 31 adjacent to the frame region NA. The common layer 41 iscommon to the plurality of pixels.

A method for manufacturing the display device 2 according to theembodiment includes the following process steps: forming the pluralityof mask spacers 32 in the frame region NA outside the pixel region DA soas to surround the pixel region DA; forming the plurality of maskspacers 31 in the pixel region DA; and bringing the mask 71 intoabutment with the mask spacers 31 to form the common layer 41 common tothe plurality of pixels onto the mask spacers 31. The mask 71 has theopening 72 that opens the pixel region DA and whose opening end 72 a hasthe undulations 73 in plan view.

This embodiment avoids contact between the opening end 72 a of the mask71 and the mask spacers 31 in any positional shift of the mask 71 thatcan occur when the mask 71 and target substrate are joined togetherclosely. Such contact avoidance prevents a foreign substance fromadhesion.

The shape of the undulations 73 is not limited to a wavy shape. Theundulations 73 need to have a shape that maintains equal to or greaterthan a predetermined distance between the mask spacers 31 in the pixelregion DA and the undulations 73 (i.e., the opening end 72 a of the mask71).

The mask spacers 31 are arranged as before in order to hold the FMMuniformly. This embodiment includes changing the shape of the openingend 72 a of the mask 71 rather than changing the arrangement of the maskspacers 31 from their previous arrangement, thus manufacturing thedisplay device 2 that has higher reliability than a conventional displaydevice.

The mask spacers 32 in the frame region NA may be arranged in such amanner that equal to or greater than a predetermined distance ismaintained between the mask spacers 32 and the undulations 73 (oropening end 72 a).

FIG. 6 schematically illustrates the relationship between each maskspacer 31 and the opening end 72 a of the mask 71 illustrated in FIG. 4.In FIG. 6, the mask spacer 31 has a diameter d1, and the opening end 72a of the mask 71 has such a wavy shape as to be, by a distance d1, awayfrom the end of the mask spacer 31, which faces the opening end 72 a.Each dent of the undulations 73 in this case forms a segment of a circlehaving a radius R expressed as d2+d1/2. Herein, let the diameter d1 beset to 10 μm; in addition, let the distance d2 be set to 50 μm byreflecting processing accuracy in the mask 71 and mask shifting. Theradius R is accordingly expressed as R=50+10/2=55 μm.

The mask 71 undergoes patterning through etching including aphotolithography and etching process from its front and back surfaces.Even at an exposure resolution of 3 μm (ghi-line) in thephotolithography, the size of the aforementioned wavy shape issufficiently large, facilitating fine processing into such a wavy shapeas described above.

With reference to FIG. 7(a), FIG. 7(b), and FIG. 11, the followingfurther details effects that are obtained by formation of a common layerusing the mask 11.

FIG. 7(a) schematically illustrates in plan view where the opening end72 a of the mask 71 in FIG. 4 shifted toward the pixel region DA islocated in relation to the mask spacers 31. FIG. 7(b) schematicallyillustrates in plan view where the opening end 72 a of the mask 71 inFIG. 4, with its protrusions, which are located between the pixel-regionmask spacers 31 adjacent to the frame region NA, being shifted towardthe mask spacers 31, which sandwich the protrusions, is located inrelation to the mask spacers 31.

FIG. 8(a) schematically illustrates in cross-sectional view where theopening end 72 a of the mask 71 in FIG. 4 disposed properly with respectto the mask spacers 31 is located in relation to the mask spacers 31.FIG. 8(b) schematically illustrates in cross-sectional view where theopening end 72 a of the mask 71 in FIG. 8(a) shifted toward the pixelregion DA is located in relation to the mask spacers 31.

The mask 71 can be replaced with a mask 81 (i.e., a CMM) having anopening 82 whose opening end 82 a has a linear shape in plan view. FIG.10(a) schematically illustrates in cross-sectional view where theopening 82 of the mask 81 disposed properly with respect to the maskspacers 31 is located in relation to the mask spacers 31. FIG. 10(b)schematically illustrates in cross-sectional view where the opening end72 a of the mask 81 in FIG. 10(a) shifted toward the pixel region DA islocated in relation to the mask spacers 31. FIG. 10(c) schematicallyillustrates in cross-sectional view what happens unfavorably when acommon layer (not shown) is formed in the situation shown in FIG. 10(b)and is then sealed with the sealing layer 6.

The opening end 72 a of the mask 71 and the opening end 82 a of the mask81, in particular, the opening ends 72 a and 82 a of the respectivemasks 71 and 81 each of which is a CMM for forming the individualfunction layers (e.g., an organic film) in the EL layer 24, are locatedclose, to the maximum extent, to the perimeter of the pixel region DAincluding the dummy pixels. As illustrated in FIGS. 8(a) and 10(a), theopening end 72 a of the mask 71 and the opening end 82 a of the mask 81can have a sticking foreign substance 91, such as a film consisting ofdeposited materials resulting from film formation, and a residueremaining unremoved after mask cleaning.

Placing a magnetic-force generating source, such as a magnet (magnetplate), onto the back surface of the target substrate for instance,followed by attracting the middle of the mask 71 or 81, which is supple,with the magnet to eliminate the gap between the mask 71 or 81 and thetarget substrate causes the magnetic force to bring the target substrateand the mask 71 or 81 into close contact with each other when the commonlayer 41 is formed.

The masks 71 and 81 have their openings each of which is greater in areathan that of an FMM. Each of the masks 71 and 81, when closely joinedwith the target substrate, is held by only the mask spacers 32, whichare disposed in the frame region NA.

The opening end 72 a of the mask 71 and the opening end 82 a of the mask81 are hence more easily bent toward the target substrate by their ownweights or the magnetic force than that of an FMM when a position shiftoccurs in closely joining the mask 71 or 81 and the target substratetogether.

For this reason, the opening end 82 a bent toward the target substratecomes into contact with the mask spacer 31 upon the mask 81 beingshifted by the magnetic force from its position shown in FIG. 10(a)toward the pixel region DA, as shown in FIG. 10(b) when the mask 81 andtarget substrate are joined together closely. The foreign substance 91on the opening end 82 a consequently transfers to the mask spacer 31.

Reference is made to an instance where the common layer 41 is such afunction layer as earlier described that is included in the EL layer 24(e.g., an organic film), and where the light-emitting element layer 5including the common layer 41 is sealed with the sealing layer 6, asillustrated in FIG. 10(c) after the common layer 41 is formed.

In a situation like FIG. 10(c), where the foreign substance 91 havingsome height is sticking on the mask spacer 31 having already someheight, the foreign substance 91 cannot be covered with the sealinglayer 6 properly and is thus partly exposed from the sealing layer 6when the light-emitting element layer 5 is sealed with the sealing layer6. This missing part forms a path of water penetration, from which waterpenetrates and reaches the light-emitting element ES, thus generating adark spot. This degrades the reliability of a display devicemanufactured using the foregoing mask 81.

In contrast, the display device in the present embodiment is configuredsuch that the opening end 72 a of the mask 71 has the undulations 73having, for instance, a wavy shape so that the opening end 72 a of themask 71 and the mask spacers 31 are away from each other by equal to orgreater than a predetermined distance. In addition, the distance g(expressed as g=R=d2+d1/2) between the opening end 72 a of the mask 71and each mask spacer 31, shown in FIG. 8(a), is designed including maskaccuracy and mask shifting. The opening end 72 a and the mask spacers 31consequently do not come into contact with each other even when the mask71 is shifted with respect to the mask spacers 31, as shown in FIGS.7(a) and (b) and FIG. 8(b). The present embodiment thus prevents removalof the foreign substance 91 from the mask 71, reducing the foreignsubstance 91 that cannot be covered with the sealing layer 6 andoffering a highly reliable display device and improved yields.

FIG. 9 illustrates in plan view where the opening end 72 a of the mask71 in FIG. 4 shifted toward the frame region NA is located in relationto the mask spacers 31. FIG. 11 illustrates in plan view where theopening end 82 a of the mask 81 in FIG. 10(a) shifted toward the frameregion NA is located in relation to the mask spacers 31.

Reference is made to FIG. 11, where the mask 81 having the opening end82 a is used as a CMM. The opening end 82 a, which has a linear shape,comes into contact with many mask spacers 32 when shifted toward theframe region NA, highly probably causing the foreign substance 91 tostick to the mask spacers 32.

Referring to FIG. 3, the display device can have a trench 21 between themask spacers 31 and 32. The trench 21 is a region where the cathode 25is in conflict with a wire DW routed in the TFT layer 4.

In this case, the common layer 41 formed using the mask 81 extends outuniformly to the frame region NA upon the opening end 82 a of the mask81 being shifted toward the frame region NA, as shown in FIG. 11. Thecommon layer 41 accordingly closes the inside of the trench 21 auniformly, increasing the area of a region where the cathode 25 cannotbe in contact with the routed wire DW.

The opening end 72 a of the mask 71 in contrast, which has theundulations 73, comes into contact with fewer mask spacers 32 than theopening end 82 a shifted toward the frame region NA does, as shown inFIG. 9 even when the opening end 72 a is shifted toward the frame regionNA as much as the opening end 82 a of the mask 81 in FIG. 11. Using themask 71 as a CMM thus prevents the foreign substance 91 from sticking tothe mask spacers 32 when compared to using the mask 81 as a CMM.

In this embodiment, the common layer 41 has at its end the undulations42 corresponding to the undulations 73, as shown in FIG. 9. Even whenthe undulations 42 are at least partly disposed in the frame region NA,the common layer 41 formed using the mask 71 as a CMM extends into thetrench 21 a to a smaller extent than the common layer 41 formed usingthe mask 81 as a CMM. This reduces the area of a region where thecathode 25 cannot be in contact with the routed wire DW.

The present embodiment consequently achieves a contact region betweenthe cathode 25 and the routed wire DW while providing a margin betweenthe opening end 72 a of the mask 71 and the mask spacers 31. Thisembodiment thus oilers the display device 2 more reliable than everbefore, the mask 71 with which such a more reliable display device 2 canbe manufactured, and a method for manufacturing such a more reliabledisplay device 2.

In this embodiment, the common layer 41 formed using the mask 71 can bea layer formed all over the pixel region DA rather than formedindividually for each pixel. Examples of the common layer 41 includefunction layers (organic or inorganic layers) disposed in the EL layer24, such as a hole injection layer, a common hole transport layer, ahole blocking layer, an electron transport layer, and an electroninjection layer. As earlier described, the common layer 41 can also be alight-emitting layer that is formed using a CMM under conditions, suchas where the light-emitting element ES is an OLED that emits whitelight, and where the light-emitting element ES is an OLED having acommon light-emitting layer common to a plurality of pixels. The commonlayer 41 can also be a capping layer that is as large as theaforementioned function layer. Further, although sides of the cathode 25defining the contact region in the frame region NA are not formed usingthe mask 71, a portion of the cathode 25 without such a contact region(sides without such a contact region) is formed using the mask 71.

FIG. 4 illustrates, by way of example only, that the undulations 73 aredisposed at all the opening ends 72 a of the mask 71. The undulations 73may be disposed at part of the opening end 72 a of the mask 71 as longas they are disposed at the opening ends 72 a of the mask 71. That is,the undulations 73 need to be disposed at at least part (i.e., at leastone of the sides) of the opening end 72 a of the mask 71.

The present invention is not limited to the foregoing embodiment and canbe modified in various manners within the scope of the claims. Thetechnical scope of the present invention includes an embodiment that isobtained in combination as necessary with technical means disclosed invarious embodiments. In addition, combining the technical meansdisclosed in the individual embodiments can form a new technicalfeature.

REFERENCE SIGNS LIST

2 display device

21 a trench (contact region)

24 EL layer

25 cathode

31 mask spacer (pixel-region mask spacer)

32 mask spacer (frame-region mask spacer)

41 common layer

42, 73 undulations

71 mask

72 opening

72 a opening end

DA pixel region

NA frame region

1. A display device comprising: a plurality of pixel-region mask spacersdisposed in a pixel region where a plurality of pixels are disposed; aplurality of frame-region mask spacers disposed in a frame regionoutside the pixel region so as to surround the pixel region; and acommon layer disposed on the plurality of pixel-region mask spacers, thecommon layer being common to the plurality of pixels, wherein the commonlayer comprises an end that has undulations in a plan view.
 2. Thedisplay device according to claim 1, wherein the undulations comprise adepression between the plurality of pixel-region mask spacers adjacentto the frame region.
 3. The display device according to claim 1, whereinthe undulations are arranged at intervals equal to intervals between theplurality of pixel-region mask spacers.
 4. The display device accordingto claim 1, wherein the undulations have a wavy shape.
 5. The displaydevice according to claim 1, wherein the undulations are at least partlylocated in the frame region.
 6. The display device according to claim 1,wherein the plurality of frame-region mask spacers are arranged atintervals smaller than intervals between the plurality of pixel-regionmask spacers.
 7. The display device according to claim 1, comprising: aplurality of first electrodes; a second electrode common to theplurality of pixels; and a function layer interposed between theplurality of first electrodes and the second electrode, wherein thecommon layer having the undulations is the function layer.
 8. Thedisplay device according to claim 7, wherein the function layer is anorganic layer.
 9. The display device according to claim 1, comprising: aplurality of first electrodes; a second electrode common to theplurality of pixels; and a function layer interposed between theplurality of first electrodes and the second electrode, wherein thecommon layer having the undulations is the second electrode. 10.(canceled)
 11. (canceled)